1. Field of the Invention
This invention relates to interface systems and more particularly to interface systems for coupling a facsimile device to a fixed wireless access type of network.
2. Description of Related Art
Radio communication devices are often being used along with or in replacement of conventional wireline telephone systems. These radio communication devices provide many advantages over wireline systems. One advantage relates to the supporting infrastructure. Radio communication systems are simpler and less expensive to deploy in comparison to conventional wireline systems. Additionally, radio communication systems often have lower maintenance costs. Finally, radio communication systems are economically feasible in those sparse areas where low demand for communication services does not justify the cost of installing a wireline network.
In a fixed wireless access system (FWA), base stations form an interface between conventional wireline networks and wireless subscriber units. A subscriber unit is a user device which contains a radio transceiver for communicating with a base station. Subscriber units are often made to be compatible with ordinary wireline telephones. Typically, an ordinary telephone is plugged into the subscriber unit through a standard telephone connector such as an RJ-11 jack in place of being connected to the public switched telephone network. For conventional telephones, such a subscriber unit allows an individual to use the ordinary wireline telephone in conjunction with the subscriber unit to place or receive a call. Unfortunately, facsimile (fax) machines do not work well when merely connected to a subscriber unit or wireless transceiver.
Fax machines posses an interface that uses analog modem tones (compliant with ITU Recommendations V.17 or V.29) and are designed to allow the fax machine to communicate over the public switched telephone network (PSTN). The messaging protocol used to exchange documents follows the standards set ITU-T Recommendation T.30 "Procedures for Document Facsimile Transmission in the General Switched Telephone Network". Collectively, the fax machines following these provisions are known as Group III (G3) Fax. These G3 fax machines are referred to herein as analog fax machines in contrast fax machines or computers which emulate fax machines which communicate over a digital medium. For example, one common digital messaging format is known as Class 2.0. In particular, data devices such as laptop and desktop personal computers often implement Class 2.0 messaging formats for the communications through wireless transceivers. There are, however, no systems or device which allow common analog fax machines to transmit in a time division multiple access (TDMA) or code division multiple access (CDMA) transmission medium. There are several technical reasons.
Current wireless transceivers are not compatible with the various analog fax protocols. For example, even if a wireless transmitter is capable of establishing a link with a fax machine, the fax machine is not designed to wait until a wireless communication link is established by the transceiver. Accordingly, the fax machine's internal logic will typically cause it to time out and drop the call while the transceiver attempts to establish a wireless communication link. For obvious reasons, this situation is unacceptable. What is needed, therefore, is an interface device capable of communicating with a fax machine and with a wireless transceiver in a manner which avoids the loss of data or the dropping of a call.